The present invention relates to a blast pipe intended primarily for introducing gas into molten metal in metallurgical processes, particularly steel manufacturing processes.
Blast pipes of the kind meant here are used for injecting gas, such as oxygen, argon or nitrogen or gas mixture into primarily molten metal in metallurgical processes, such as when producing steel in electrosteel furnaces. Applications are also found where there is injected a mixture of gas and solid substances for metallurgical use.
Such blast pipes are normally made of steel. The blast pipe in use is subjected to high stresses as a result of high temperatures, erosion, oxidizing environment etc., various attempts having been made to reduce the high consumption of blast pipes, this consumption being related to the aforesaid stresses to which the blast pipes are subjected and resulting from the melting and oxidation etc. thereof.
In this respect blast pipes are known in which the outer parts of the blast pipe have been alloyed by diffusion with aluminium and thereafter coated with at least one ceramic protective layer. Blast pipes which comprise a plurality of substantially ceramic layers are also known. The manufacture of these known blast pipes is associated with considerable cost. For example, the process of alloying with aluminium is effected in separate furnaces or ovens at relatively high temperatures. As will be understood, the cost of providing the ceramic layer or layers is also high. The task of providing non-brittle alloying layers and applied coatings is also difficult to accomplish and requires the application of particular measures. Brittleness results in the phenomenom of cavitation and decreases the useful life of the blast pipe.